Convertible Senior Notes (Details) (USD $)	0 Months Ended
	Nov. 03, 2014	Dec. 31, 2014	Nov. 03, 2014
Convertible Senior Notes
Interest payable on Senior Convertible Debentures		$ 2,500,000
Amortization schedule
Deferred financing costs, Balance at the end of the period		12,336,000
Convertible Senior Notes Due 2019
Convertible Senior Notes
Aggregate principal amount (in dollars)	200,000,000		200,000,000
Interest rate (as a percent)	7.50%		7.50%
Additional aggregate principal amount pertaining to the over-allotment option granted (in dollars)	25,000,000		25,000,000
Net proceeds from offering (in dollars)	187,300,000
Interest payable on Senior Convertible Debentures	2,500,000		2,500,000
Repurchase price (as a percent)	100.00%
Conversion rate (as a percent)	0.3215434
Conversion price (in dollars per share)	$ 3.11		$ 3.11
Required consent of holders (as a percent)	66.67%
Beneficial conversion feature	0
Amortization schedule
Deferred financing costs at issuance		12,747,000
Less: Accumulated amortization		(411,000)
Deferred financing costs, Balance at the end of the period		$ 12,336,000